Richard Simpson

I will be taking delivery of a 1995 WRX on friday. It has a Blitz dump valve that has been fitted in Japan. If anyone has some knowledge of it(or dump valves in general) I would appreciate some advice:

What effect does this have on engine performance and reliability?

Is a UK Scooby dump valve any quieter or have a perfromance disadvantage?

I am not sure if it has been fitted purely to increase sound effects or to make a difference to performance.

igratton

Interesting subject.

I just installed a 'vent to atmosphere' dump valve to my motor (97MY). Things to remember are :

* Makes the pppiiissshhhhttt ! noise when you back of the gas.

* Made my car run rich and back fire all the time (often with flames)

* pi**ed my girlfriend of and I quote 'can your next Impreza be a quiet one'...I can't see the problem...I only have a humble SS Backbox, Downpipe and K&N induction kit

It was fun on the track (ask people who we in the pit lane at donnington on Sunday...they will remember it) but I've taken it off again now thru fear of blowing the tailpipe from my lovely exhaust.

Let me know how you get on.

Look at the Northern Dyno day post in the events section and 'Venting Dump/Blow-off Valves - will the ppssshht lead to a bang ? ' in this Forum

Regards

Ian

Richard Simpson

Thanks for the pointers. However it doesn't appear that both of our questions have been answered yet:

Will it damage the engine?

As I haven't really got to grips with the car yet (2 days till delivery) so I will let you know about backfires etc as they (hopefully don't) happen.

More importantly I think this topic has opened a can of worms that needs seriously addressing:

Can there be a balancing of the dump valve pssst and the girlfriends moaning?

I think this may become an issue for me very soon!!

Thanks for the help

Rgrds.


Richard

Andy Banks

I'd advise against installing an externally venting blow off valve. AFAIK, the mass air flow sensor measures the air flow before the blow off valve. When you change gears or backoff the throttle, the blow off valve vents the air externally, but the air flow sensor isn't able to measure this. Hence the car runs too rich and backfires. Backfiring will probably kill your catalytic converter.

If you do decide to get one, APEXi sell a version with adjustable volume control for your girlfriend.

Andy
WRX STi4

DYNT

You won't get any HP increase by installing external venting BOV.
BOV is to protect your inducer from shattering or backspin. It will also improve throttle responce.
Engine Damage- Not that I know off but U might ended up loosing engine performance.

If U could get hold of the MY99 WRX BOV ..new design and better.

I hate the aftermarket BOV sound. Toooo loud.

Stef

Just take the Blitz dump valve off.
Problem solved!!!

Stef.

Richard Simpson

Thanks guys

I think I will remove the Blitz dump valve. Anybody know where I can get one of the MY99 WRX dump valves and the price?

Gethin

Got a HKS Sequential BOV on MY96 WRX and IMHO it has made difference in throttle response. I can now back off the throttle going flat into a bend and then on exit have instant turbo again.

Seems the HKS is very well made compared to the crappy ones I have seen around.

It does make a loud whoosh....but on the HKS this can be tweaked to give a different sound. It does make my Magnex pop a bit more downhill with throttle released or between 2nd and 3rd slow change, but not much, no nasty backfires. The car is also set up to run lean, so I cannot comment on the previous lean/rich comment, and I did not do a PE rolling road run before the BOV was fitted.

Gethin.

Dave Mitchell

I have the same opinion as Gethin....

I have HKS SQV on a MY93. I`ve never had any problems with back firing. It`s not been on a RR since i fitted it.
No problems what so ever.....

Dave
Well untill i fit me HKS full exhaust with down pipe....